Read write device for optical memory and method therefore

ABSTRACT

A method and miniaturizable device is described to read/write information to an optical storage medium ( 11 ). A device comprises one or more light sources ( 12 ) bounded up with an access unit ( 10 ) which is arranged to be controllable to a position, in which light beams ( 21, 22 ) are transmitted transversal towards an optical storage medium, and reflected light beams ( 33 ) are analysed by a detector element ( 18, 26 ) which further informs the access unit whether to move or stand still to keep light beams in focus and on track. A device according to the invention is possible to implement in a small size and low weight due to reduced component count and thin access unit geometries. A communication device ( 80 ) according to the invention may be implemented to fulfil a crucial need for ultraminiature range of communication devices.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is for entry into the U.S. national phase under §371for International Application No. PCT/FI02/000954 having aninternational filing date of Nov. 27, 2002, and from which priority isclaimed under all applicable sections of Title 35 of the United StatesCode including, but not limited to, Sections 120, 363 and 365(c).

TECHNICAL FIELD OF THE INVENTION

The present invention relates to the field of optical storage systems,and more particularly to reading out information from an optical storagemedium and to writing information onto the optical storage medium.

BACKGROUND OF THE INVENTION

An optical storage system is composed of an optical disc drive systemand an optical storage medium, such as an optical disc. The optical discdrive has a light beam source, a light beam distribution system and alight beam detection system for reading out information from the opticaldisc and recording information onto the optical disc. The read and writeoperation functionality of the optical disc drives is traditionallyaccomplished by using an optical pick-up unit (OPU) which is arranged tolocate so that the light beam is angled perpendicular to the opticaldisc for radiating and detecting purposes. This kind of read and writeoperation is designated as the perpendicular operation in this presentapplication.

The optical pick-up units of prior art typically have a laser lightemitting diode, light detector, optical lens and device e.g. voice coilto position the lens for proper focusing and tracking during read andwrite operation. The OPU moves radially to access data tracks on theoptical disc by using a sliding rail system connected to a motor or thefixed OPU is connected to a geared rotatably positioned optical pipeconnected to a motor. When the optical disc rotates around its center bymeans of a motor and the OPU or a light guide head connected to the OPUmoves radially across the optical disc, data tracks of the optical discare accessed.

The optical pick-up units of prior art typically use a single light beampath toward the optical storage medium. Optical light guides are used asa channel for directing the light beam from the light source to the lenssystem adjacent to the track of the optical disc and for directing backthe reflected light beam from the track of the optical disc to thedetection system adjacent to the light source. In a typical embodiment,a polarizing beam splitter (or similar system using e.g. semi-reflectingmirrors) is used to direct the light beam to the lens system.

The traditional CD and DVD technology is considered to be known art andcovered extensively by patents and published literature; hence, it isnot mentioned here explicitly. Some examples of non-standard solutionsfor prior art optical pick-up units are described in the followingdocuments: WO 99/00793, U.S. Pat. Nos. 4,581,529, 5,481,515, 5,835,458and 6,256,283. Recent prior art for non-standard fixed-arm systemsincludes documents WO 02/059888A2 and WO 02/059887A2.

There are certain limitations related to the OPU systems of prior art. Amass of the movable OPU or the geared rotatably positioned optical lightguide head is heavy. Especially a laser source is a weighty andlarge-size component and the mass of the laser source is centered on themovable OPU or the movable light guide head in prior art systems. Theweight of the movable OPU causes together with the pitching motion ofthe disc problems in defocussing and sensitivity to the track angleerror. Many optical storage systems of prior art require astigmatism inthe system for error analysis, and this also results in higher componentcount in the form of used astigmatism elements. All extra componentscause weight increase and complexity to the system which extends accesstimes and increases power consumption of the OPU system. The accesstimes are outstandingly long in case of the movable sledge OPU systems.

SUMMARY OF THE INVENTION

An object of the present invention is to solve the problems related toprior art and thus to provide a device and method for reading out datafrom the optical storage medium and writing data to the optical storagemedium enabling a small-size and low-weight optical storage system.Another object of the invention is to provide a method and device forreading out data from the optical storage medium and writing data to theoptical storage medium to keep an optical storage system in focus and ontrack to ensure a reliable operation.

The object of the present invention is fulfilled by providing a deviceand method where a single light beam or multiple light beams arearranged to be angled transversal to the optical storage medium forradiating (emitting) the beams and detecting (receiving) the reflectedbeams. The beam is transversal when its centre beam essentially deviatesfrom the perpendicular direction to the optical storage medium.

In accordance with the present invention there is provided a devicecomprising an optical storage medium drive and at least one access unitfor reading out data from and writing data to an optical storage mediumcomprising a plurality of data tracks, said device comprising: at leastone light source arranged to produce at least one first light beam andat least one second light beam; transmitting means arranged to transmitand guide said first light beam and said second light beam towards saiddata tracks of the optical storage medium; and detecting means arrangedto detect light beams that are reflected from the surface of the opticalstorage medium, is characterised in that said access unit is arranged topivot on one end three-dimensionally, said transmitting means and saiddetecting means are arranged to move in accordance with the movement ofsaid access unit, said transmitting means are arranged to guide saidfirst light beam and said second light beam transversal towards datatracks of the optical storage medium, and said detecting means arearranged to receive the reflected beams of said first light beam or saidsecond light beam from said data tracks of the optical storage medium.

In accordance with the present invention there is provided a method forreading out data from and writing data to an optical storage medium in adevice comprising at least one access unit, the method comprising steps,in which: at least one optical storage medium comprising a plurality ofdata tracks, stores data; an optical storage medium driver controlsoperation of the device; at least one light source produces at least onefirst light beam and at least one second light beam; said first lightbeam and said second light beam are transmitted and guided towards saiddata tracks of the optical storage medium; and the light beams that arereflected from the surface of the optical storage medium are detected,is characterised in that it further comprises steps, in which: saidfirst light beam and said second light beam are guided transversaltowards said data tracks of the optical storage medium; the reflectedbeams of said first light beam or said second light beam from said datatracks of the optical storage medium are received; and said access unitis moved three-dimensionally in relation to a pivot point on one end tofocus and track said first and second light beams.

One preferred embodiment of the present invention is considered to be acommunication device and a method where an access unit, preferably anarm unit, is controllable to a position, in which a read light beam isdirected transversal towards data tracks of the optical storage mediumand write light beam perpendicular to said data tracks of the opticalstorage medium, and in which the light beam is kept in focus and ontrack by following a change in the intensity distribution of thereflected light beam identified by a detector. According to onepreferred embodiment a light source emitting light beams locates at ornear a pivot point on one end of the access unit.

In this application three-dimensionally means that the access unit movesin relation to vertical (x) and horizontal (y) axis and rotates inrelation to longitudinal (z) axis at the pivot point. In thisapplication a term focusing signifies same as keeping in focus and aterm tracking signifies same as keeping on track.

The present invention provides a novel way of implementing the opticalread/write system which enables to reduce component count by a newoptical component arrangement which simplifies the optical system. Themoving access unit according to the present invention is possible tomanufacture using thinner geometries and thus the moving acces unitfulfils the requirements of small size and low weight which are crucialneeds in the ultraminiature range of optical storage devices.

In addition, the present invention provides a novel and accurate way ofkeeping the optical read/write system in focus and on track. Thecombination of using transversal light beams to be directed to andreflected from the optical storage medium and the use of the movingaccess unit provides a simple focusing and tracking method. Thefocus-error and track-error signals can be identified by following thechange in the intensity distribution of the reflected light beam. Thereliable operation is achieved by the simultaneous transversal lightbeam focusing and tracking during the read and/or write operation.

In addition, a smaller size and lower weight of the moving access unitaccording to the present invention also enables faster random accesstime of the optical storage device. The movable mass of the access unitbecomes still lighter by fixing all possible components (including alight source) onto the pivot point of the access unit. This minimizesthe angular momentum needed to move the arm. By reducing component countthe method and device according to the invention thus reduces powerconsumption. The component count of optical components can be minimizedin the simplest implementation of the present invention significantly.Due to reduced component count space savings are also achieved andproduction costs become lower.

Further the device and method according to the present invention doesnot put any additional restrictions on the optical storage medium andall existing optical disc media can be used.

Some embodiments of the present invention are described in the dependentclaims. The main physical characteristics and simulation results for theinvention are also described in the attached report, which supplementsthe patent application but does not supercede it. The report containssome detailed calculations which have been left out of this application,as they are considered details of one specific embodiment rather thanpertaining to the basic invention. However, they are relevant forestablishing the technical feasibility of the invention.

The novel features which are considered as characteristic of theinvention are set forth in particular in the appended Claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawings andalso the attached report.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a illustrates a side projection of the device according to oneembodiment of the present invention.

FIG. 1 b illustrates a side projection of the device according toanother embodiment of the present invention.

FIG. 2 a illustrates an embodiment of an optics set up of the deviceaccording to the invention.

FIG. 2 b illustrates another embodiment of an optics set up of thedevice according to the invention.

FIG. 2 c illustrates another embodiment of an optics set up of thedevice according to the invention.

FIG. 3 a illustrates an simple embodiment of an optics set up of thedevice according to the invention.

FIG. 3 b illustrates another embodiment of an optics set up of thedevice according to the invention.

FIG. 4 a illustrates one embodiment of the device according to theinvention.

FIG. 4 b illustrates another embodiment of the device according to theinvention.

FIG. 4 c illustrates still another embodiment of the device according tothe invention.

FIG. 5 illustrates an embodiment of using two separate light sourcesaccording to the present invention.

FIG. 6 a illustrates a fundamental idea of a focusing signal detectionof the device according to the invention.

FIG. 6 b illustrates a fundamental idea of a focusing signal detectionof the device according to the invention.

FIG. 6 c illustrates a fundamental idea of a focusing signalidentification of the device according to the invention.

FIG. 6 d illustrates a fundamental idea of a focusing signalidentification of the device according to the invention.

FIG. 6 e illustrates a fundamental idea of a focusing signalidentification of the device according to the invention.

FIG. 7 a illustrates a fundamental idea of a tracking signal detectionof the device according to the invention.

FIG. 7 b illustrates a side view of a fundamental idea of a trackingsignal detection of the device according to the invention.

FIG. 7 c illustrates a side view of a fundamental idea of a trackingsignal detection of the device according to the invention.

FIG. 7 d illustrates a simplified fundamental idea of a tracking signalidentification of the device according to the invention.

FIG. 7 e illustrates a simplified fundamental idea of a tracking signalidentification of the device according to the invention.

FIG. 7 f illustrates a simplified fundamental idea of a tracking signalidentification of the device according to the invention.

FIG. 7 g illustrates a top view of a fundamental idea of a trackingsignal identification of the device according to the invention.

FIG. 7 h illustrates a fundamental idea of a tracking signalidentification of the device according to the invention.

FIG. 7 i illustrates a fundamental idea of a tracking signalidentification of the device according to the invention.

FIG. 7 j illustrates a fundamental idea of a tracking signalidentification of the device according to the invention.

FIG. 7 k illustrates a fundamental idea of a tracking signalidentification of the device according to the invention.

FIG. 8 illustrates a block diagram of a communication device accordingto the invention.

FIG. 9 illustrates a flow diagram of a method according to theinvention.

FIG. 10 a illustrates a flow diagram of an algorithm for a methodaccording to an embodiment of the invention.

FIG. 10 b illustrates a flow diagram of an algorithm for a methodaccording to another embodiment of the invention.

DETAILED DESCRIPTION

FIG. 1 a illustrates a principal set up of the device according to thepresent invention for reading out data from an optical storage mediumand for writing data to an optical storage medium. The optical storagemedium 11 can be any CD-type readable and/or writeable optical disc,such as CD-R, CD-ROM, CD-RW, DVD or any other existing optical discmedia or future implementations of this kind. The optical storage medium11 comprises data tracks, and adjacent data tracks are decoupled fromeach other by a narrow area. The data tracks may be pre-grooved orstamped and made of suitable material to form optically resolvablestructures on the optical storage medium. Bit patterns that produceadequate optical intensity variation on the data tracks, e.g. the pittedstructure of the medium, form a basis for storing and changinginformation. The device also comprises an optical storage medium drive(not depicted), which can be of any commercial type available. Themovement of the optical storage medium is arranged by the opticalstorage medium drive.

The access unit 10 pivots on its one end 101, which is called here apivot point 101, three-dimensionally. Three-dimensionally means that theaccess unit moves in relation to vertical (x), horizontal (y) andlongitudinal (z) axis at the pivot point. Thus the access unit iscapable of being controlled in upwards-downwards and lateral directionin relation to its pivot point, as well as in direction of rotationrelated to axis of revolution in relation to the pivot point of theaccess unit. By controlling the access unit in relation to the tilted (zaxis) direction the push-pull movement of the access unit is produced,which push-pull movement keeps the z axis perpendicular to the surfaceof the optical storage medium. The access unit 10 may preferably be anarm unit, which may also be called a pivoting arm or moving arm. Themotion of the arm in the x,y,z directions may be controlled e.g. byacoustic loops similar to those controlling the motion of the smalllenses in traditional CD drives. The access unit can be realized in anumber of alternative ways; the key point is that orientation of thebeam must be controllable in the x, y, and z directions.

Other main units of the device illustrated in FIG. 1 a are a lightsource 12 for emitting a light beam 13, an optical component 15, such asa mirror, prism or other suitable optical component, for bending thelight beam towards the optical storage medium 11, another opticalcomponent 16, such as a lens or diffractive optical element (DOE), forbending and focussing the light beam, an optical component 17, such as alens or diffractive optical element (DOE), for collimating and/orfocussing the reflected light beam and a detector element 18 forreceiving and detecting the reflected light beam. The detector element18 has two or more, preferably four, detecting surfaces for analysingfocus and tracking signals. Collimating optics 14 may be used forcollimating the light beam. The transmission of the light beam 13 fromthe light source 12 to the optical components 15, 16 can be done in freespace, but it is also possible to use an optical component (notdepicted), such as a waveguide, lightguide or alike, for transmittingthe light beam. All above mentioned units 12-18 of the device arearranged so that they move in accordance with the movement of the accessunit 10, i.e. they are hung to the access unit with appropriatefastenings means an example of which is a supporting body 19 in FIG. 1a. The units 12 and 18 are also connected electrically to the accessunit 10 and a main control unit (not depicted) of the device. The lightsource 12 is preferably located at or near the pivot point 101 in orderto minimize the angular momentum needed to move the arm.

In accordance with the above mentioned set up of the device according tothe present invention the light beam emitted from the light source isguided in a transversal angle towards the data tracks of the opticalstorage medium. The reflected light beam reflected from the surface ofthe optical storage medium is received in a transversal angle by thedetector element 18 and associated optical components 17. Due to thedifferent optical paths of the light beams, the separation of theillumination light and the reflected light containing the data signal isoccuring naturally.

According to one embodiment of the device a light source 12 may belocated at the other end of the access unit 10 than the pivot point 101,i.e. at the access unit, preferably an arm unit, head. In thisembodiment the light source is directed in an appropriate angle towardsa surface of an optical storage medium and thus no mirror 15 is neededfor bending a light beam. Only a DOE 16 is needed to focus a light beamproperly. This embodiment requires less components than depicted in FIG.1 a, but it presumes very low weight of a light source to be used.

FIG. 1 b illustrates another embodiment of the device according to thepresent invention. In this set up of the device the detector element 18is located at or near the pivot point 101 and the light source 12. Whenusing a single light path propagation of the light beam it is needed inaddition to provide another optical component 15 b after the focusingcomponent 17 a to bend the light beam towards the detector element 18.There may also be provided detecting optics 14 b in front of thedetector element for focusing the reflected light beam.

According to another embodiment of the device also multiple light pathsmay be used. FIG. 1 b illustrates a splitter component 17 b forsplitting the light beam into more than one beam. When the splittercomponent is used there is needed detector optics 14 b in front of thedetecting element for each beam of the multiple light beams 13 b. Inthis embodiment the light source 12 may emit a single or multiple lightpaths 13 a depending on the type of the light source. In case of thelight source emits a single light path 13 a the splitter component 17may be installed in front of the bending component 15 a.

FIGS. 2 a-2 c illustrate optics set up of the device according to someembodiment of the present invention where two light beams 21, 22 areused: one for reading data 21 and the other for writing data 22 (thickerlines). The optics set up of the device comprises mirrors 24, 25 forbending the light beams. Instead of mirrors, also prisms or othersuitable optical components may be used for bending the light beams. Onthe substrate 23 are integrated a detector element 26, transparentelement 28 e.g. glass element and diffractive elements (DOE) 27 in frontof the transparent element. The reflected light beams 33 are directedtowards the detector element 26. In embodiments depicted in FIGS. 2 aand 2 b the mirror for the light beam 21 is ahead of the mirror 24 forthe light beam 22 so that the read beam 21 is arranged to form a spotlocation 29 b of the focussed beam on the optical storage medium 11 in adifferent location than the other spot location 29 a of the focussedbeam formed by the write beam 22. According to an embodiment there areseparate spot locations for the both focussed beams, namely the readingpoint 29 b and the writing point 29 a. These spot locations 29 a, 29 bmay locate to any direction in relation to each other on the datatracks, including location on different tracks, e.g. the other maylocate ahead, behind or aside in relation to the other. According to thepreferred embodiment of the invention the read beam 21 is arranged toform a spot location 29 b of the focussed beam on the optical storagemedium 11 preferably slightly ahead of the other spot location 29 a ofthe focussed beam formed by the write beam 22.

FIG. 2 a shows one embodiment of the invention that uses the transversallight beams both for reading data and for writing data in relation tothe optical storage medium. As shown in FIG. 2 b another embodiment ofthe invention uses the transversal light beam for reading data and theperpendicular light beam for writing data in relation to the opticalstorage medium. Transversal means here transversal beam towards theoptical storage medium and perpendicular means perpendicular beam to theoptical storage medium. The synchronization of beam pulses are describedlater in this description. The synchronization of read and write pulsesenable the focus and write operation to take place simultaneously. Thisembodiment enables fast random access times for writing operation. Itprovides an extremely small and low-mass optical pick-up unit which is acrucial need in ultraminiature device range and enables fast access.Also due to reduced component count it reduces costs and decreases powerconsumption.

FIG. 2 c illustrates another embodiment of the optics set up of thedevice using two light beams according to the invention. In thisembodiment the read beam 21 and write beam 22 hit the same spot location29 of the focussed beams. The set up of optics differs from the set upshown in FIG. 2 a or 2 b in that the mirror 24 is ahead of the mirror25. As shown in FIG. 2 c this embodiment of the invention uses thetransversal light beam for reading data and the perpendicular light beamfor writing data in relation to the optical storage medium. Inconsequence of that the focus and track guiding is done by thetransversal light beam at the same time when writing operation is doneby the perpendicular light beam. The synchronization of read and writepulses are described later in this description. This embodiment of theinvention also provides an extremely small and low-mass optical pick-upunit which is a crucial need in ultraminiature device range. Also due toreduced component count it reduces costs and decreases powerconsumption.

FIG. 3 a shows an embodiment of a simple optics set up of a deviceaccording to the invention, where separate read 31 and write beams 32and reflected read beam 33 are guided through a single lens 35. Thediffractive element (not depicted) can be realized as a surface element.Also this embodiment of the invention uses the transversal light beamfor reading data and the perpendicular light beam for writing data inrelation to the optical storage medium.

FIG. 3 b illustrates an embodiment of the optics set up of the deviceaccording to 5 the invention, where separate read beam 31 and write beam32 and reflected read beam 33 are guided through a single lens 35. Thediffractive element (not depicted) can be realized as a surface element.In addition optical components 36, 37 are used to separate incoming readbeam 31 and reflected read beam 33 from write beam 32 by polarization orwavelength of the beams. The optical component 36, 37 can be realized byusing components, such as polarizing splitters and dichroic beamsplitters, and in association with these components diffractive elementscan be used. This embodiment provides that read and write beams haveopposite polarization or different wavelengths and that the mediumresponds differently to light at these different polarizations orwavelengths (e.g. two-photon operation).

FIG. 4 a illustrates an embodiment of the device according to theinvention with one access unit 41 which is preferably an arm unit. Inthis embodiment the read beam and write beam is controlled along the arm41 pivoting on one end the pivot point 101 three-dimensionally asdescribed earlier. The arm unit is run by a small-size and low-weightmotor 43. According to this embodiment the read beam is guided andbended to meet the optical storage medium 11 in transversal angle, andthe write beam is guided and bended perpendicular to the optical storagemedium 11. In association with one arm implementation all the optics setups described in FIGS. 2 a, 2 b, 3 a and 3 b may be used. Thisarrangement enables simultaneous read and write operation. It alsoenables very fast random access time for read operation even if writeoperation is slower.

FIG. 4 b illustrates an embodiment of the device according to theinvention with double-arm unit. In this embodiment the read beam iscontrolled along the first arm 41 and the write beam is controlled alongthe second arm 42. Both arms pivot on one end of the pivot point 101three-dimensionally. According to this embodiment the read beam isguided and bended to meet the optical storage medium 11 in transversalangle, and the write beam is guided and bended transversal orperpendicular to the optical storage medium 11. In association withdouble-arm implementation all the optics set ups described in FIGS. 2 a,2 b, 3 a and 3 b may be used. This arrangement enables simultaneous readand write operation. It also enables very fast random access time forread operation even if write operation is slower. The double-arm unitalso enables to use separate read-only drives and read/write drives,analogously to existing CD and CD-R drives. The double-arm solution,however, adds some weight to the device, but the extra mass can beminimized by sharing some functions of the motor 43 e.g. by the gearsystem so that it is not necessarily required to include two separatemotors for both arms. The arms can be synchronized mechanically toprovide more symmetric read and write operation.

Still a further embodiment of the device according to the invention isillustrated in FIG. 4 c. Here, a traditional sledge unit 45 is used inassociation with the arm unit 41 as access units according to oneembodiment of the invention. In this embodiment the read beam is guidedand bended to meet the optical storage medium 11 in transversal angle bythe arm unit 41, and the write beam is guided and bended perpendicularto the optical storage medium 11 by the sledge unit 45. The arm unitpivots on one end the pivot point 101 three-dimensionally. Thisembodiment adds more weight to the device than the one-arm unit depictedin FIG. 4 a and the double-arm unit depicted in FIG. 4 b, becauseseparate motors 43, 44 are needed for the sledge unit 45 and arm unit41. Although the motors 43, 44 may be integrated in one module, theirfunctionality is different. The embodiments shown in FIGS. 4 b and 4 care not regarded the best mode of the invention, because they addweight, cost and complexity to the device and the write operation usestraditional optical pick-up units (OPU) as shown in FIG. 4 c with theirproblems described in the backgroud of the invention.

FIG. 5 illustrates an embodiment of the present invention, whereseparate light beams or beam paths 56, 58 are produced by two separatelight sources 51, 52. The light beam paths 56, 58 are guided accordingto the invention to the access unit 50 as described earlier in thisdescription. In this embodiment the separate light sources 51, 52 aresynchronized by the synchronization means 55 to insure high level ofprecision in read/write operation. A flow diagram of the simplifiedalgorithm for the embodiment with separate light sources embodiment isdescribed in FIG. 10 a and a flow diagram of another algorithm for theembodiment with separate light sources is described in FIG. 10 b.

In the following the detection of the focusing and tracking signals isdescribed. The light beam is transmitted from the light source along anpivoting arm which is capable of being controlled three-dimensionally inrelation to its pivot point. This means that the pivoting arm moves inup-and-down, lateral and longitudinal (rotational related to axis ofrevolution) directions, i.e. it pivots on in relation to x-, y- andz-axis. This arrangement ensures that the light beam follows the datatrack transversal to the surface of optical storage medium in thedirection of propagation but accurately perpendicular to the surface ofthe optical storage medium in lateral direction. A push-pull movement ofthe access unit keeps the z axis perpendicular to the surface of theoptical storage medium.

The combination of using transversal light beam to be directed to andreflected from the optical storage medium and the use of the moving armprovide simple focusing and tracking capability, because focusing andtracking signals can be identified by following the change in theoptical intensity distribution of the reflected light beam. Realiableoperation and fast random access times are achieved by the simultaneoustransversal light beam focusing and simultaneous read and/or writeoperation.

The signal processing method relies on the existence of several ordersof diffracted light. The reflected light beam is separated intosub-beams, called diffraction orders and assigned by their ordinalnumbers starting from the central beam (diffraction order=0) andappended by plus or minus sign on the repective sides of the centralbeam (×1, +1, etc.). The central beam (the thick arrow 1 b, 1 b′ inFIGS. 7 b and 7 c) is the zero-order diffraction, corresponding toordinary geometric reflection. In the first approximation, geometricoptics can be used to analyze the behavior of this order (FIGS. 6 a-6e). Analysis of the side orders (the thin lines 1 a, 1 c, 1 a′, 1 c′, 1c″ in FIGS. 7 b, 7 c) requires optical modelling where the diffractionis taken into account. However, again as a first approximation,geometric optical modelling has been used to trace the location of thecentral peak of the diffracted orders. The central beam and side orderstogether form the so-called “baseball pattern” (FIGS. 7 g-7 k) known inprior art.

FIGS. 6 a and 6 b illustrate the fundamental idea of the focusing signaldetection of the device according to the invention. A detector element18 which may preferably be a quad detector with four detector surfaces18 a, 18 b, 18 c and 18 d is depicted in FIGS. 6 c-6 e (and 7 d-7 f). InFIG. 6 a the access unit 10, preferably the arm unit, moves relative tothe optical storage medium 11 as needed to keep the light beam in focus.FIG. 6 b shows an optical element e.g. a lens 16 which bends the lightbeam transversal towards the optical storage medium, and a detectorelement 18 with at least two surface elements. More detectors anddetectors with different geometries may also be used. According to theinvention the optical element 16 and the detector element 18 arearranged to move along the arm unit 10 with appropriate fastening means.In consequence of the moving arm the movement of the optical element 16toward or away from the optical storage medium will move the spotlocation A, B, C on the detector element 18 according a distance betweenthe optical storage medium 11 and the optical element 16. The points A′,B′, C′ are spot locations of the beams on the optical storage medium,respectively. In FIG. 6 b the spot location A (and A′) shows thesituation when the reflected light beam is in focus on the surface ofthe optical storage medium 11. Correspondingly the spot location B (andB′) shows that optical storage medium 11 is too close to the detector(above focus) and the spot location C (and C′) shows that it is too farfrom the detector (below focus). The light beam may optionally be guidedto the detector element 18 with an optical element (e.g. FIG. 2 a part28) or a diffractive optical element (e.g. FIG. 2 a part 27) in front ofthe detector.

The detection by identifying the focusing signal to control the movementof the arm unit is described next in association with FIGS. 6 c, 6 d and6 e. These figures illustrate a detector element 18 , preferably a quaddetector with four detector surfaces 18 a, 18 b, 18 c, 18 d. A trackdirection is shown by an arrow. For example, a collimated circular lightbeam can be emitted and then be focussed on the data layer by adiffractive optical element. The reflected light beam is then collimatedor focused on the detector by the diffractive optical element. Thereflected light beams from the surface of the optical storage medium arereceived by the quad detector 18 which four surface areas 18 a, 18 b, 18c and 18 d responding to light intensity signals S1, S2, S3 and S4,respectively. FIGS. 6 c, 6 d, 6 e shows if one received reflected lightbeam is in focus or not. The intensity distribution and the shape of thespot on the detector 18 varies at various positions of the opticalstrorage medium. The focus is determined by the location of the centralreflected beam along the top-bottom direction of the quad detector.(There are additional diffracted orders that appear as side spots. Sincethese are used in the tracking detection, they have been eliminated fromthis figure; in principle they only add extra calibrating factors to thefocus push-pull algorithm). In FIG. 6 c a focusing signal aligns to thespot 76 which covers an area where the surface area S2 is much largerthan the surface area S3. This means that the reflected light beam isabove focus and the detector element is arranged to control the accessunit to move downwards. In FIG. 6 d a focusing signal aligns to the 76which covers an area of the detector surfaces where the signals S2 andS3 are equal. This means that the reflected light beam is in focus andany correction is not needed and thus the detector element is arrangedto control the access unit to stand still. Finally, in FIG. 6 e afocusing signal aligns to the spot 76 which covers an area where thesignal S2 is much smaller than the signal S3. This means that thereflected light beam is below focus and the detector element is arrangedto control the access unit to move upwards. The baseball pattern on thesurface of the detector is moving in accordance with changed focus.

FIGS. 7 a, 7 b and 7 c illustrate a highly simplified schematic of thefundamental idea of the tracking of the device according to theinvention. A more realistic schematic is shown in FIGS. 7 g-7 k. FIGS. 7a-7 f show an intuitive representation of one embodiment of the basicconcept. In FIG. 7 a the access unit 10, preferably the arm unit, movesin lateral direction in relation to the optical storage medium 11 tokeep the light beam on track. FIGS. 7 b and 7 c show a lens 16 whichforms a focused beam that on reflection creates two orders ofdiffraction around the central beam. In a geometrical approximation,these can be modelled as beams 1 travelling towards the data track 70 ofthe optical storage medium 11. Each beam is then reflected towards adetector element 18 with at least two, preferable four, surface elementsfor analysing tracking. The reflected central beam in FIG. 7 b is 1 band in FIG. 7 c 1 b′. Respectively, the reflected diffracted beams are 1a, 1 c and 1 a′, 1 c′. FIG. 7 b shows a situation when the light beam ison track (diffracted orders −1, 0, +1) and FIG. 7 c shows an off tracksituation where the light beam 1 c′ is reflected from the edge (beam 1c″) of the data track 70.

The detection by identifying the tracking signal to control the movementof the arm unit according one simplified embodiment of the invention isdescribed next in association with FIGS. 7 d, 7 e and 7 f. These figuresillustrate a detector element 18, preferably a quad detector with fourdetector surfaces 18 a, 18 b, 18 c, 18 d. A track direction is shown byan arrow. For example, a circular collimated light beam 1 can befocussed on the data layer by a diffractive optical element. Thereflected light is then collimated or focused on the detector by thediffractive optical element. The tracking signal is detected by thedetection element 18. The spot locations of the reflected beams form abaseball pattern on the four surfaces of the detector. The intensitydistribution and the shape of the spot on the detector 18 varies atvarious positions of the optical strorage medium. By comparing theintensities received by e.g. two quadrants, e.g. surfaces 18 a and 18 dlocating at opposite sides of the track, the tracking characteristicscan be identified. The reflected light beams (FIG. 7 b beams 1 a, 1 b, 1c) from the surface of the optical storage medium are received by thequad detector 18 which four surface areas 18 a, 18 b, 18 c and 18 dresponding to light intensity signals S1, S2, S3 and S4, respectively.For example, in FIGS. 7 d, 7 e and 7 f two reflected light beams aredetected and identified. In case of the off track situation, thebaseball pattern becomes asymmetric according to FIGS. 7 d and 7 f. InFIG. 7 d the light intensity of the spot 77 a is higher on the area ofthe detector surface 18 a than the intensity of the spot 77 b on thesurface 18 d, corresponding to signal S1 being higher than signal S4,which means that the light beam is to the left of the track. Thisresults that the detector element 18 is arranged to control the accessunit to move to the right. In FIG. 7 f the intensity of the spot 77 b ishigher on the area of the detector surface 18 d than the spot 77 a on 18a, corresponding to signal S4 being higher than signal S1, which meansthat the light beam is to the right of the track. This results that thedetector element 18 is arranged to control the access unit to move tothe left. In FIG. 7 e intensities of the spots 77 a and 77 b are equalin the surface area 18 a and 18 d, corresponding to signal S1 beingequal to signal S4, and thus the light beam is on track. No correctionis needed and thus the detector element is arranged to control theaccess unit to stand still. The baseball pattern on the surface of thedetector is moving in accordance with changed tracking.

The details of the reflected spot and baseball pattern will differsomewhat from the idealized situation described above; for example,rather than staying exactly circular, the central focused beam will bedeformed when it is above or below focus. In addition, it is necessaryto use a more realistic diffraction model (described below) to describethe readout mechanism more realistically. The method shown above workswell as a qualitative first approximation. When the push-pull mechanismof the arm unit is used, these irregularities are not critical; thesystem aims to keep the system in that configuration in which thecentral spot is focused on the center of the quad detector and the sidebaseball patterns are symmetrical. At worst, the irregularities mayrequire adjustments to the sensitivity of the push-pull mechanism indifferent directions, and also some asymmetric calibration of thesignals from the quad detectors (which can be done trivially in thesignal-processing electronics). Similarly, the detector may becomeslightly misaligned from the track because of the motion of the arm;this can be corrected for by similar calibrations or in some cases evenignored.

A more physically accurate presentation of the readout scheme utilizinga more realistic diffraction model is now shown. The detection byidentifying the tracking signal to control the movement of the arm unitaccording to this embodiment of the invention is described next inassociation with FIGS. 7 g-7 k.

The tracks of the data layer are forming a periodical structure whichfunctions as a reflection grating as shown in FIG. 7 g, which is a topview of FIG. 7 b. FIG. 7 g illustrates tracks 70 and the grating periodt depicted as the track separation. This grating is separating theincoming beam 1 into sub-beams 1 a, 1 b and 1 c, which are calleddiffraction orders, and assigned by their ordinal numbers starting fromthe centre beam 1 b and appended by minus sign 1 a or plus sign 1 c onthe respective sides of the centre beam. FIG. 7 g shows threediffraction orders from −I to +I, where I is 1, 2, 3, etc. The trackingsignal is generated by taking the advantage of the interference betweenthe 0^(th) (reflected centre beam 1 b) order and ±Ith order, whichchanges the intensities received by the quadrants 18 a and 18 d as shownin FIGS. 7 h-7 j. It should be noted here that the coherent light isused and so the intensities of the overlapping orders cannot be simplyadded together, instead the interference between the orders must betaken into account when calculating the overall intensities of thequadrants.

FIGS. 7 h-7 j illustrate a detector element 18, preferably a quaddetector with four detector surfaces 18 a, 18 b, 18 c, 18 d. A trackdirection is shown by an arrow. A tracking signal is used to follow thedata tracks during the playback of the optical storage medium. Onemethod to produce the tracking signal in an access unit is to comparethe light intensities received by two guadrants of the detector element18, assigned with detector surface 18 a responding to the signal S1 anddetector surface 18 d responding to the signal S4, where 18 a and 18 dare located at the opposite sides of the track. In general a geometry ofthe optical storage medium defines in which one of the two quadrants theintensity is increasing and decreasing when the spot is focussed on theside of the track. The +Ith orders are partly overlapping with the 0thorders as shown in FIGS. 7 h-7 j, as well as in FIG. 7 g, and areforming a baseball pattern on the detector element 18. FIG. 7 i shows asituation when the spot 77 is focused in the middle of the track. Thensignals S1 and S4 in the quadrants 18 a and 18 d, respectively, areequal because the situation is symmetrical and so the interference ofthe 0^(th) order with the −Ith and +Ith order is identical. Now if thespot 77 is focussed on the side of the track it changes the phases ofthe reflected sub-beams 1 a or 1 c on the detector. Depending on thestructure of the optical storage medium, and on which side of the trackthe beam is, either −Ith or +Ith order is interfering constructivelywith the 0^(th) order, i.e. the light intensity in that quadrant isincreasing. The other order is interfering destructively with the 0^(th)order and so the light intensity in that quadrant is decreasing.Consequently, as shown in FIG. 7 h, the destructive interference in thequadrant 18 a gives lower signal than the constructive interference inthe quadrant 18 d, which means that the intensity signal S4 is higherthat the intensity signal S1, and hence the light beam is to the left ofthe middle of the track. Correspondingly, as shown in FIG. 7 j, theconstructive interference of the quadrant 18 a giving higher signal thanthe destructive interference of the quadrant 18 d, which means that theintensity signal S1 is higher than the intensity signal S4, and hencethe light be is to the right of the middle of the track. The magnitudeof the constructive and destructive interference, and thus the signal,in the quadrants of the detector is proportional to the spot's 77distance from the track causing a signal that varies in the function ofthe distance. The imbalance of the quadrant intensities can be detectedand used to generate the tracking signal needed to keep the beamfocussed on the track.

The rotation of the access unit, preferably an arm unit, changes thealignment of the detector and the tracks and the system must be able totolerate this. The misalignment can be optimised to be less than 10degrees and the system can be designed to tolerate this. Themisalignment is changing the intensity distribution on the detectorsymmetrically as shown in FIG. 7 k. The equal areas of the spots andthus intensities of the +Ith and −Ith orders are shifted from thequadrants 18 a and 18 d to the quadrants 18 b and 18 c. Due to this therelative intensities between the quadrants 18 a and 18 d, used tocalculate the tracking signal, and relative intensities between thequadrants 18 b and 18 c, used to calculate the focusing signal, are notchanging and the signals can be calculated as usual. In FIG. 7 c themisalignment is exaggerated and normally will be less than 10 degrees inaccordance with tests performed.

In the preferred embodiment, the same light beam is used to provide boththe focusing and tracking signals. Also three-beam or multi-beam orother types of steering may be used to provide the focusing and trackingsignals. The device of the invention is not highly sensitive to theangle error caused by movement of the access unit, because the baseballpattern is simply slightly rotated.

The focusing and tracking signals can be studied by simulations, such asfunctional electric simulation signal calculations, by using e.g. a quaddetector element with four surface elements. A detailed calculation ofthe actual signals and the sensitivities and calibrations needed toperform the push-pull operation requires diffractive modelling ratherthan the simplified geometric model shown here. However, addingdiffraction to the model affects only the detailed results and not thefundamental principle. Note that in a real system there may beadditional optical phenomena not covered here such as additionaldiffraction from the edges of the groove; since these are second-orderphenomena, they are likely to be insiginificant. In cases where they arenot, they can be handled by additional signal processing; the specificsignal processing depends on the details of the particular embodiment,and is not covered here.

FIG. 8 illustrates a communication device 80 comprising an opticalstorage medium drive 81 and at least one access unit 83 for reading outdata from an optical storage medium 82 and for writing data to anoptical storage medium 82 according to the invention. The communicationdevice also comprises at least one light source 84 for emitting lightbeams, optical components 85 for transmitting, guiding, bending andfocussing the light beams and a detector element 86 for detecting thereflected light beams. Light sources 84, e.g. semiconductor lasers, areused to provide light beams needed to read and write data from/to theoptical storage medium 82. When the light beam is emitted from the lightsource it may diverge, i.e. the emitted light beam widens. In order totransfer enough light from the light source to the desired distanceoptical components 85 are used to restrict the widening of the lightbeam. As well, optical components 85 are used to collimate or focus theemitted light beam. The collimated light beam can be used to propagatethe beam long distances in free space and the focusing can be used toimage the beam into a lightguide or wave-guide. Also optical components85 are used to redirect and focus the light beam to the data track ofthe optical storage medium. In front of the detector optical components85 are used to collect the reflected light beam to the detector element.These optical components, here just referred by a number 85, arediscussed more detail in connection with FIGS. 1 a, 1 b, 2 a, 2 b, 3 aand 3 b.

In FIG. 8, in accordance with shown in FIGS. 1 a and 1 b, the accessunit 83 pivots on its one end (pivot point) three-dimensionally inrelation to vertical (x), horizontal (y) and longitudinal (z) axis. Thusthe access unit is capable of being controlled at least inupwards-downwards, lateral and tilted direction in relation to its pivotpoint. The access unit 83, optical components 85 and the detectorelement 86 for receiving and detecting the reflected light beam are thesame as described in association with FIGS. 1 a, 1 b, 2 a and 2 b. Theyare arranged so that they move in accordance with the movement of theaccess unit, i.e. they are fixed to the access unit with appropriatefastenings means. The units 84 and 86 are also connected electrically tothe access unit 83 and a main control unit (not depicted) of the device.The light source 84 is preferably located at or near the pivot point ofthe access unit. In accordance with the above mentioned set up of thedevice the light beam emitted from the light source is guided in atransversal angle towards the data tracks of the optical storage medium.The reflected light beam reflected from the data tracks of the opticalstorage medium is received in a transversal angle by the detectorelement 86 and associated optical components 85. All the embodiments ofthe device described earlier in association with FIGS. 1 a to 5 are alsorelevant with the communication device 80 according to the invention.Also the fundamental idea of the focus error correction (FIG. 6) and thetrack error correction (FIGS. 7 a and 7 b) are relevant in associationwith the communication device according to the invention.

According to one further embodiment of the invention the light source 84may be located at the other end of the access unit than the pivot point,i.e. on the access unit head, and the light beam from the light sourceis guided in a transversal angle towards data tracks. Thisimplementation reduces still component count, because the mirror 15, 15a (FIGS. 1 a and 1 b) can be omitted and for focusing the light beam thediffractive optical element DOE 16 (FIGS. 1 a and 1 b) can be used.However, this implementation requires smaller-size and lower-weightlight sources than available by today's technology.

FIG. 9 illustrates a flow diagram of a method according to the presentinvention for reading out data from an optical storage medium andwriting data to an optical storage medium. In the first step 901 thelight source produces the light beam. If two or more separate lightsources are used, the light beams are synchronized by synchronizing thelaser sources according to step 903. The synchronization algorithm usedis described later in this description. In step 905 emitted light beamsmay be collimated before transmitting them in step 907. The emittedlight beams are guided and bended transversal towards the tracks of theoptical storage medium according to step 909. After this the reflectedlight beams from the tracks of the optical storage medium aretransmitted in step 911 and then the reflected light beams are detectedin step 913. The focus error is detected according steps 915 and 916 andif correction is needed, appropriate correction is made by a movement ofthe access unit according to step 919 and after that steps 909 to 916are repeated. The track error is detected according steps 917 and 918and if correction is needed, appropriate correction is made by amovement of the access unit according to step 920 and after that steps909 to 918 are repeated. When focus and tracking is correct the readand/or write operation using transversal angled light beams is performedaccording to step 921.

Note that the control in the z-direction has been left out of thisdefinition of the algorithm as not presenting any significant novelty;it is a straightforward push-pull algorithm which keeps the beamcorrectly aligned by seeking symmetry of the reflected signal. Note alsothat the sampling frequencies for control in the various directions(x,y,z) may be very different, and as such FIG. 9 is only a highlyidealized representation of the actual algorithm (in which sampling inthe sampling rates for the x, y, and z directions may be different).However, this idealization adequately presents the significant featuresof the invention, and the refinements are considered specificembodiments.

It is also possible to derive more complex algorithms based onsimultaneous analysis of the various push-pull loops (in the x, y, and zdirection). These are considered specific extensions and refinements ofthe present invention, and are not covered in detail.

FIG. 10 a illustrates the synchronization algorithm of the methodaccording to the invention, if two separate light sources are used.Separate initialization routine may be needed. In first step 111 thefirst light source is switched on, and then in step 113 the location ofthe light beam of the first light source is detected. It is furtherchecked in step 115 that location is on track and in step 117 that thelocation is at focus. If the answer in steps 115 and/or 117 is negative,the appropriate corrections are made according to steps 116 and 118. Instep 119 the second light source is turned on, and in consequence thefirst light source may be turned off or it is kept on constantly. Theoperation of the second light source is executed in step 120 and aftersuccesful operation 121 the second light source is turned off in step123. After this the first light source (is turned on) and continues theoperation it was doing before interruption. As an exemplary embodimentof the method according to the invention is the situation, that thefirst light source is used for read operation and the second source forwrite operation. According to this example the read beam may be pulsedso that it is off when the write beam is turned on, or it can be kept onconstantly. The energy-optimal and thermally optimal pulsingimplementation depends on details of the physical implementation.

Also the use of other kind of synchronization algorithms are possible.FIG. 10 b describes a synchronization algorithm of another embodiment ofa method according to the invention, if two separate light sources areused. Separate initialization routine may be needed. In first step 131the first light source is switched on, and then in step 133 the locationof the light beam of the first light source is detected. It is furtherchecked in step 135 that location is on track and in step 137 that thelocation is in focus. If the answer in steps 135 and/or 137 is negative,the appropriate corrections are made according to steps 136 and 138. Instep 139 the second light source is turned on, and in consequence thefirst light is kept on but a read/write operation is interrupt for acertain time period. The operation of the second light source isexecuted in step 140 untill said time period is elapsed according step141 and 142. Now in step 143 the first laser source continues read/writeoperation from the location where it was when the operation wasinterrupt and the read/write operation of the second light source isinterrupt. According to this embodiment both laser sources are on atsame time.

According to the invention other embodiments with one or more lightbeams of the kind described earlier are also possible, and they arestraightforward extensions of these, but they are not covered in detailhere.

The invention is not restricted to the embodiments described above.While a preferred embodiment of the present invention is disclosedherein for purposes of explanation, numerous changes, modifications,variations, substitutions and equivalents in whole or in part should nowbe apparent to those skilled in art to which the invention pertains.Accordingly, it is intended that the present invention be limited onlythe characteristics and scope of the hereto appended claims.

1. A device comprising: an optical storage medium drive; an opticalstorage medium comprising a plurality of data tracks; at least oneaccess unit for reading out data from and writing data to said opticalstorage medium; a single light source arranged to produce at least onefirst light beam and at least one second light beam; optics arranged totransmit and guide said first light beam and said second light beamtowards said data tracks of the optical storage medium; and a detectorarranged to detect light beams that are reflected from the surface ofthe optical storage medium, wherein said access unit is arranged topivot on one end at a pivot point in order to move three-dimensionallyin relation to the pivot point, said optics and said detector arearranged to move in accordance with the movement of said access unit,said optics are arranged to guide said first light beam transversaldirectly to data tracks of the optical storage medium in accordance withthe movement of said access unit, and said detector is arranged toreceive the reflected beams of said first light beam or said secondlight beam from said data tracks of the optical storage medium in orderto control the movement of said access unit.
 2. A device according toclaim 1, wherein said access unit is arranged to be movable to aposition, in which said first light beam and said second light beamtransmitted from said optics towards said data tracks of the opticalstorage medium form a first point and a second point on said data tracksof the optical storage medium where the reflected light beams aredetected to be in focus and on track by said detector.
 3. A deviceaccording to claim 2, wherein said first point is arranged to be locatedin a different location than said second point on said data tracks ofthe optical storage medium.
 4. A device according to claim 2, whereinsaid first point is arranged to be located slightly ahead of said secondpoint on said data tracks of the optical storage medium.
 5. A deviceaccording to claim 2, wherein said first point and said second point arearranged to be located in a same intersection point on the track of theoptical storage medium.
 6. A device according to claim 1, wherein saidoptics are arranged to guide said first light beam transversal directlyto said data tracks of the optical storage medium, and said second lightbeam perpendicular to said data tracks of the optical storage medium. 7.A device according to claim 6, wherein said first light beam is arrangedto read out data from said data tracks of the optical storage medium andsaid second light beam is arranged to write data to said data tracks ofthe optical storage medium.
 8. A device according to claim 1, wherein atleast one light source is arranged to be located at or substantialproximity of the pivot point of said access unit.
 9. A device accordingto claim 1, wherein said optics comprise at least one first opticalcomponent for bending said first light beam and said second light beamtowards said data tracks of the optical storage medium, and at least onesecond optical component for bending and focusing said first light beamand said second light beam transversal directly to said data tracks ofthe optical storage medium.
 10. A device according to claim 9, whereinsaid optics further comprise collimating optics for said light source,splitting optics for splitting the emitted light into multiple lightbeams and focusing optics in connection with said second opticalcomponent.
 11. A device according to claim 9, wherein said first opticalcomponent and said second optical component are arranged to be a singlelens for bending and focusing said first light beam transversal directlyto said data tracks of the optical storage medium and said second lightbeam perpendicular to said data tracks of the optical storage medium.12. A device according to claim 9, wherein said first light beam andsaid second light beam are arranged to have opposite polarizations. 13.A device according to claim 9, wherein said first light beam and saidsecond light beam are arranged to have different wavelengths.
 14. Adevice according to claim 1, wherein said detector comprises at leastone detector element for detecting the reflected light beams of saidfirst light beam or said second light beam, and a third opticalcomponent for bending and focusing said reflected light beams of saidfirst or second light beam.
 15. A device according to claim 14, whereinsaid detector further comprises a fourth optical component for bendingthe reflected light beams of said first light beam or said second lightbeam towards said detector element, focusing optics in front of saiddetector element and splitting optics for splitting said reflected lightbeams of said first light beam or said second light beam into multiplelight beams.
 16. A device according to claim 14, wherein said detectorelement comprises at least two detector surfaces for detecting thefocusing signal and tracking signal of the reflected light beams of saidfirst light beam or said second light beam.
 17. A device according toany of claims 14, wherein said detector element is arranged to detect bysaid detector surface of said detector element at least one focusingsignal and at least one tracking signal of the reflected beams of saidfirst light beam or said second light beam received from the surface ofthe optical storage medium, and said detector element is arranged tocontrol the movement of said access unit according to said focusingsignal and said tracking signal detected by said detector surface tokeep said first light beam and said second light beam in focus and ontrack.
 18. A device according to claim 14, wherein said detector elementis arranged to detect by said detector surface of said detector elementidentifying a change in the intensity distribution of at least onefocusing signal and at least one tracking signal of the reflected beamsof said first light beam or said second light beam received from thesurface of the optical storage medium, and said detector element isarranged to control the movement of said access unit by following saidchange in the intensity distribution to keep said first light beam andsaid second light beam in focus and on track.
 19. A device according toclaim 15, wherein said focusing optics in front of said detector elementcomprises diffractive optical elements.
 20. A device according to claim1, wherein said optics and said detector further comprise a waveguide orlightguide arranged to transmit said first and second light beam and/orsaid reflected light beams of said first light beam or said second lightbeam along said access unit.
 21. A device according to claim 1, whereinsaid access unit is an arm unit.
 22. A device according to claim 1,wherein the device comprises a first access unit for reading out datafrom the optical storage medium, and a second access unit for writingdata to the optical storage medium, wherein said first access unit andsaid second access unit is one of the following: an arm unit, a sledgeunit or any combination of an arm and sledge unit.
 23. A deviceaccording to claim 1, wherein said device is a communication device. 24.A device comprising: an optical storage medium drive; an optical storagemedium comprising a plurality of data tracks; at least one access unitfor reading out data from and writing data to said optical storagemedium; at least one light source arranged to produce at least one firstlight beam and at least one second light beam; optics arranged totransmit and guide said first light beam and said second light beamtowards said data tracks of the optical storage medium; and a detectorarranged to detect light beams that are reflected from the surface ofthe optical storage medium, wherein said access unit is arranged topivot on one end at a pivot point in order to move three-dimensionallyin relation to the pivot point, said optics and said detector arearranged to move in accordance with the movement of said access unit,said optics are arranged to guide said first light beam and said secondlight beam transversal directly to data tracks of the optical storagemedium in accordance with the movement of said access unit, and saiddetector is arranged to receive the reflected beams of said first lightbeam or said second light beam from said data tracks of the opticalstorage medium in order to control the movement of said access unit. 25.A device according to claim 24, wherein said first light beam isarranged to be produced by a first laser source and be transmitted by afirst light beam path; said second light beam is arranged to be producedby a second laser source and be transmitted by a second light beam path;and said first laser source and said second laser source are arranged tobe synchronized by a synchronizer.
 26. A device according to claim 25,wherein said first light beam path and said second light beam path arearranged to use the same first and second optical components.
 27. Amethod, comprising: producing at least one first light beam and at leastone second light beam by a single light source; transmitting and guidingsaid first light beam and said second light beam towards data tracks ofan optical storage medium; and detecting the light beams that arereflected from a surface of the optical storage medium wherein thedetecting comprises: moving an access unit three-dimensionally inrelation to a pivot point on one end to focus and track said first andsecond light beams; guiding said first light beam transversal directlyto said data tracks of the optical storage medium three-dimensionally inaccordance with the movement of said access unit; and receiving thereflected beams of said first light beam or said second light beam fromsaid data tracks of the optical storage medium three-dimensionally inaccordance with the movement of said access unit.
 28. A method accordingto claim 27, wherein said access unit is controllable to a position, inwhich said first light beam and said second light beam transmitted andthe reflected light beams of said first light beam or said second lightbeam detected, to form at least one first focused beam and at least onesecond focused beam on said data tracks of the optical storage medium onthe basis of said first light beam, said second light beam and saidreflected light beam of said first light beam or said second light beam.29. A method according to claim 28, wherein said first focused beamforms at least one first point and said second focused beam forms atleast one second point on said data tracks of the optical storagemedium.
 30. A method according to claim 29, wherein said first point islocated in a different location than said second point on said tracks ofthe optical storage medium.
 31. A method according to claim 29, whereinsaid first point is located slightly ahead of said second point on saidtracks of the optical storage medium.
 32. A method according to claim29, wherein said first point and said second point are located in a sameintersection point on the track of the optical storage medium.
 33. Amethod according to claim 27, wherein said first light beam istransmitted and guided transversal directly to said data tracks of theoptical storage medium, and said second light beam perpendicular to saiddata tracks of the optical storage medium.
 34. A method according toclaim 33, wherein said first light beam reads out data from and saidsecond light beam writes data to said data tracks of the optical storagemedium.
 35. A method according to claim 27, wherein at least one firstoptical component bends said first light beam and said second light beamtowards said data tracks of the optical storage medium, and at least onesecond optical component bends and focuses said first light beam andsecond light beam transversal directly to said data tracks of theoptical storage medium.
 36. A method according to claim 35, whereincollimating optics collimates said light source, splitting optics splitsthe emitted light into multiple light beams and focusing optics inconnection with said second component focuses light beams.
 37. A methodaccording to claim 35, wherein said first optical component and secondoptical component is a single lens that bends and focuses said firstlight beam transversal directly to said data tracks of the opticalstorage medium and said second light beam perpendicular to said datatracks of the optical storage medium.
 38. A method according to claim35, wherein said first light beam and said second light beam haveopposite polarizations.
 39. A method according to claim 35, wherein saidfirst light beam and said second light beam have different wavelengths.40. A method according to claim 27, wherein at least one detectorelement detects the reflected light beams of said first light beam orsaid second light beam and a third optical component bends and focusessaid reflected light beams of said first light beam or said second lightbeam.
 41. A method according to claim 40, wherein a fourth opticalcomponent bends said reflected light beams of said first light beam orsaid second light beam towards said detector element, focusing optics infront of said detector element focuses and splitting optics splits saidreflected light beams of said first light beam or said second light beaminto multiple light beams.
 42. A method according to claim 40, whereinsaid detector element comprises at least two detector surfaces fordetecting the focusing signal and tracking signal of the reflected lightbeams of said first light beam or said second light beam.
 43. A methodaccording to claim 40, wherein said detector element detects by saiddetector surface of said detector element at least one focusing signaland at least one tracking signal of the reflected beams of said firstlight beam or said second light beam received from the surface of theoptical storage medium, and said detector element controls the movementof said access unit according to said focusing signal and said trackingsignal detected by said detector surface to keep said first light beamand said second light beam in focus and on track.
 44. A method accordingto claim 40, wherein said detector element detects by said detectorsurface of said detector element identifying a change in the intensitydistribution of at least one focusing signal and at least one trackingsignal of the reflected beams of said first light beam or said secondlight beam received from the surface of the optical storage medium, andsaid detector element controls the movement of said access unit byfollowing said change in the intensity distribution to keep said firstlight beam and said second light beam in focus and on track.
 45. Amethod according to claim 27, wherein said access unit is an arm unit.46. A method according to claim 27, wherein a first access unit readsout data from the optical storage medium, and a second access unitwrites data to the optical storage medium, wherein said first and saidsecond access unit is one of the following: an arm unit, a sledge unitor any combination of an arm and sledge unit.
 47. A method according toclaim 27, wherein said device is a communication device.
 48. A method,comprising: producing at least one first light beam and at least onesecond light beam by at least one light source; transmitting and guidingsaid first light beam and said second light beam towards data tracks ofan optical storage medium; and detecting the light beams that arereflected from a surface of the optical storage medium wherein thedetecting comprises: moving an access unit three-dimensionally inrelation to a pivot point on one end to focus and track said first andsecond light beams; guiding said first light beam transversal directlyto said data tracks of the optical storage medium three-dimensionally inaccordance with the movement of said access unit; and receiving thereflected beams of said first light beam or said second light beam fromsaid data tracks of the optical storage medium three-dimensionally inaccordance with the movement of said access unit; a first laser sourceproduces said first light beam and a second laser source produces saidsecond light beam; and said first laser source and said second lasersource are synchronized, a first laser source and a second laser sourceare initialized separately, said first laser source turns on, said firstlaser source emits said first light beam and a first point is locatedfor read/write operation, a location of said first point is analyzed, afocusing and tracking of said first point is analyzed, said second lasersource turns on, said second laser source emits said second light beamand a second point is located for read/write operation, and said secondlaser source turns off after said read/write operation.
 49. A methodaccording to claim 48, wherein said second laser source turns onresulting said first laser source to go in an interrupt mode for apredetermined time period to said first point, and said first lasersource continues read/write operation from said first point after thepredetermined time period and said second laser source goes in aninterrupt mode.
 50. An apparatus comprising: means for driving anoptical storage medium comprising a plurality of data tracks; at leastone means for accessing data configured to read out data from and writedata to said optical storage medium; integral means for supplying lightconfigured to produce at least one first light beam and at least onesecond light beam; means for optically processing light configured totransmit and guide said first light beam and said second light beamtowards said data tracks of the optical storage medium; and means fordetecting configured to detect light beams that are reflected from thesurface of the optical storage medium, wherein said means for accessingdata is configured to pivot on one end at a pivot point in order to movethree-dimensionally in relation to the pivot point, said means foroptically processing light and said means for detecting are configuredto move in accordance with the movement of said means for accessingdata, said means for optically processing light is configured to guidesaid first light beam transversal to data tracks of the optical storagemedium in accordance with the movement of said means for accessing data,and said means for detecting is configured to receive the reflectedbeams of said first light beam or said second light beam from said datatracks of the optical storage medium in order to control the movement ofsaid means for accessing data.
 51. A method, comprising: producing atleast one first light beam and at least one second light beam by atleast one light source; transmitting and guiding said first light beamand said second light beam towards data tracks of an optical storagemedium; and detecting light beams that are reflected from a surface ofthe optical storage medium wherein the detecting comprises: moving anaccess unit three-dimensionally in relation to a pivot point on one endto focus and track said first and second light beams; guiding said firstand second light beams transversal directly to said data tracks of theoptical storage medium three-dimensionally in accordance with themovement of said access unit; and receiving the reflected beams of saidfirst light beam or said second light beam from said data tracks of theoptical storage medium three-dimensionally in accordance with themovement of said access unit.